. Author manuscript; available in PMC: 2019 Apr 10.

Published in final edited form as: Expert Opin Ther Targets. 2018 Apr 10;22(4):353–363. doi: 10.1080/14728222.2018.1451514

Table 1.

Current classification of CD4+FOXP3+ human Treg^a

Cell subset	Phenotype	Functional characteristics
Fraction 1: Naïve Treg (nTreg)	CD4⁺CD45RA⁺FOXP3^low CD25^hiCD127^low CTLA4^low	Weak suppressor activity; proliferate and differentiate into effector Treg upon TCR stimulation
Fraction 2: Effector Treg (eTreg)	CD4⁺CD45RA^-FOXP3^hi CD25^hiCTLA-4^hi PD1⁺TIM-3⁺GITR⁺ Fas⁺IL-10⁺TGF3⁺	Strong suppressor activity; prone to apoptosis; low stability Increase with age
Fraction 3: Non-Treg	CD4⁺CD45RA^-FOXP3^low IL2⁺IFN3⁺IL17⁺	No suppressor activity

Human CD4+FOXP3+ T cells are phenotypically and functionally heterogeneous. Based on expression levels of FOXP3 and CD45RA, they can be divided into three subsets [12]